CF-Duck Pond-CS 960125 214488~882
Consulting Engineers DATE: {/2 6-'/'~'~
12000 ~or~ l~d, Sui~c 180 21,t/455-3880
Dallas. ~cxu 7~3~ Fax 2141~8g-~882 T~: ~; ~
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1-2S-1996 2:0SPM FROM JONES/CARTER-DALLAS 21~4883882 P. 2
l~,e,c, ommend~tion~i
In consideration of the conditions found at the site, as well as gcotechnical and
environmental assessments performed in and around the pond, Jones & Carter, Inc. presents
several recommendations for consideration by the City regarding the Duck Pond and the
park as a whole.
Silt Removal
The existing depth of the pond/s of serious concern duc to thc propensity of oxygen levels
to decrease, temperature to fluctuate and algae blooms to form in shallow bodies of water.
Should no improvements to the pond be undertaken in the near term, we would predict
increasing difficulty maintaining the fish population in the pond even considering the
positive effects of the fountains. Therefore we recommend the city consider a plan to
remove the accumulated silt from the bottom of the pond and restore the pond to its original
depth or possibly increase the depth somewhat.
As a minimum, we recommend that the pond be restored to what appears to be it~ original
average depth of approximately 4.0 feet with a maximum depth of 6.0 feet. While it would
be desirable to make the pond deeper overall, the potential depth is limited by the existing
clay liner. Should the City desire to deepen the pond, thc clay liner will need to be
removed and replaced in order to minimize thc possibility of the pond water leachiRg into
the sub-strata and reducing the water level during dry periods. Due to our understanding of
budgetary constraints at this time, we do not recommend any pond excavation beyond that
necessary to restore thc overall depth to an average of 4.0 feet.
In performing the silt removal, two methods are available including in-situ (wet) removal or
dry removal. Wet removal is most often associated with dredging of large channels, lakes
or bays using Iarge barge mounted drag lines or pumping equipment. Due to the small size
of the pond and the relatively small amount of silt to be removed, this method will probably
be impractical by traditional means. One option for wet removal will be thc usc of a small
pontoon boat mounted backhoe which will serve the same purpose as a dragline but reduce
costs due to mobilization expenses for this size of a project. Should the excavation be
performed in-sim, we city prepare plans specifications
recommend
that
the
construction
and
based upon a performance standard in lieu of specifying construction methods in order to
allow interested contractors to propose the most econora.~cal method for silt removal. This
method will be than traditional excavation duc to the
substantially
more
expensive
inefficiencies associated with wet excavation, difficult working conditions and wet hauling
costs. In addition, cor~truetion time will be approximately double that of dry excavation for
a similar quantity of material. Based preliminary opinions of probable construction
upon
cost (see Appendix A), in-sim excavation of the silt will have a project cost of $73,340.
Should the following plan for protection of the ducks and f'~h for dry excavation be
acceptable, the City may consider dry excavation of the pond. The definition of "dry"
excavation should be clarified for the purposes of this report because the excavated material
will not be truly dry, only more manageable and able to be handled with available
excavating equipment and trucks without special modification. If the pond were drained, or
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1-23-1996 2:06PM FROM JONES/CARTER-DALLAS 2144883882 P. 3
partially drained, the City could benefit from reduced construction cost due to more efficient
methods of excavation, reduced hauling costs and less construction time overall. In
addition, the excavation could be more easily controlled to reduce the possibility of
penetrating the clay pond liner while maximizing the available depth. Based upon
preliminary opinions of probable construction cost (see Appendix A), dry excavation of the
silt will have a project cost of $~5,740.
In any proiect involving thc r~moval of the silt from thc pond, disposal of the excavated
material must be considered. Based upon the environmental and ge, otechaical reports, the
excavated material will be of medium to high plasticity, extremely loose, highly moist and
relatively inert environmerttally. This type of material is best disposed of by landfilling as
opposed to on-sit~ disposal for several reasons. The silt will b~ difficult to compact when
placed, will probably not support veletation if used for top soil, and will take some time to
dry. In addition, because of potential anaerobic conditions, the odor of the drying material
may be significant when considered in a residential area for an extended period. However,
due to the lack of adverse constituents, thc materials will not need special handling for
disposal or necessarily need to be taken to a sanitary landfill if appropriately documented.
Therefore, we again recommend that the City pr~are construction plans and specifications
based upon a performance standard in lieu of sp~ifying disposal methods in order to allow
interested contractors to propo~ the most economical method for hauling and disposal. The
cost projections in Appendix A include reasonable costs for silt disposal based upon thee
parameters.
Protection of Ducks and Hsh
As we committed in our proposal and throughout the process, any undertaking at Duck
Pond Park will consider the impact upon the duck and fish population. For the construction
phase of the project we must consider the n~d to maintain a water body for the ducks as
well as a suitable environment for the fish to survive if possible. The protection of the
ducl~ is the simplest undertaking and should consist of the following:
· The installation of protective fencing Or mesh around all construction activities including
appropriate barriers across the water.
· The maintenance of a portion of the pond at all times for the ducks to exist and seek
protection from predators.
· Thc maintcnancc of access by the ducks to the duck shelter and nesting areas. We feel
relatively confident that feeding issues at thc duck pond will be taken care of by city
staff and area residents.
The protection and maintenanc~ of the fish population is somewhat more difficult, however,
due to the disruption that will occur during construction. Shoald in-sim silt removal be
performed, the water will become quite murky duc to thc stirring of silt from the bottom
during removal. This disturbance will affect the ability of the fish population to survive due
to water clarity and oxygen availability. Should dry removal be performed, the obvious
concerns for maintenance of a water body exist for the fish population.
.
JONES & CARTER. I,~IC.
1-25-1996 2:06Pf-I FROM JONES/CARTER-DALLAS 214&883882 p.&
In consideration of both the duck and fish population,s, we recommend the installation of a
low water dam across the neck of the pond at the outset of construction. This dam will
minimize the travel of silt laden water throughout the pond for in-sim silt retaoval and will
allow for maintenance of a relatively undisturbed water body at all times. Upon completion
of the remediation work on one side of the dam, the duck population may be relocated to the
opposite side of the dam and construction may continue on the other side. Should dry
excavation be undertaken, the low water dam may be used to impound water on one side or
the other in order to allow for maintenance of the water body at all times. The contractor
may pipe or pump water around the dry side of the dam during construction to facilitate
drainage needs, but wouId have the means to maintain a portion of the lake at all times. For
this arrangement, the fmh population might be able to be "herded" into the undisturbed
water body to some degree, but under even the best circumstances we anticipate the loss of
fish due to construction.
In the interest of restoring the fish population of the pond upon completion of construction,
we have make contact with Mr. Clell Guest of the Inland Fisheries Office of the Texas
Parks and Wildlife Department, to inquire about the stocking of fish. Upon description of
r. he project and situation, Mr. Guest has stated that his department would restock the pond
with channel catfish and hybrid sunfish next summer at no cost to the City. This restocking
could be done after completion of the project and would undoubtedly increase the number of
fish in lhe pond. Therefore, we believe that it may be prudent to discount the value of
maintainin~ the fish popuhtion during conswaction due to the complexities involved and
plan on restocking the pond upon completion.
Protection of Public and Park Grounds
In the construction of the project, another concern will be the protection of the general
public and the park grounds as a whole. In order to facilitate these concerns, we
recommend that the following st.ps be taken as a part of any construction project:
* The contractor shall install protective fencing around the construction staging and
operating areas and maintain the security of the same at all times.
* The City shall define and limit the construction area to be utilized by the contractor in
order to minimize the impact on the recreational value of the park during construction
and the possibility of damage to existing trees and park improvements.
The contractor shall be required w restore any gromxis and/or improvemen~ damaged
or impacted during construction to a condition as good or better than it existed prior to
construction. In order to document and assure this takes place, we recommend that a
pictorial or video record be made of the park immediately prior to commencement of
construction.
10
,IONE8 & CARTER, INC.
1-~D-1~6 ~:OTPM FROM JONES/CARTER-DALLAS 2]44883882
Erosion Control
As identified above, there are three primary areas in which erosion control measures should
be considered in the park as a part of this project. For each area there will be a number of
alternatives to consider both from a functional engineering perspective as well as the
aesthetic appeal of the improvements. The alternatives available for all appliea~ion~ include:
· Stabilized Fill - Placement of stabilized fill in a controlled manner to restore areas where
erosion has occurred. This alternative will be the most economical to construct but the
life span will be the least. As erosion has occurred previously, it can be assumed that
the till wouId erode again over time.
· Fill with Geotextile l::abric - Placement of fill can be improved by thc use of a geotcxtile
fabric or grid to stabilize the fill beyond what may be accomplished otherwise. This
application is particularly suited for arca~ where water will not be passing over it with
any significant velocity, such as shorelines, but is not suited for higMy erosive
applications such as creek channels over the long term.
· Concrete Lining with Surface Treatment - The most conventional erosion control
method is the placement of concrete lining. However, due to aesthetic considerations,
we would not recommend this unless a surface treatment such as exposed aggregate or a
stamped pattern was included. This may be the most economical structural solution, but
is also the least aesthetically pleasing f'mal product.
· Gabions - The city has recently used a gabion lined channel immediately north of Bethel
School Road on a channel improvement project with great success. This method may be
considered for selected areas near the existing storm drain outfalls and the lake
discharge, however, due to the relatively low height of the eroded areas, standard
gabions may be too large to be utilized throughout the project. Gabion mattresses may
be a consideration for channel lining both upstream and downstream of the pond,
however, due to their relatively low expense as compared with concrete lining. The
primary drawback to gabion mattresses is the maintenance consideration of such an
installation in the flowline of a channel.
· Rock wall~ and Channel - The installation of rock perimeter walls and channel lining is
without a doubt the most aesthetically pl~a~ing alternative, but also the most expensive.
There are examples of rock walls throughout Coppell on virtually every water body
constructed recently, and an example of the same where the lake discharge drops to pass
under Bethel School Road. From an aesthetic consideration, this is the best alternative.
· Rip rap stone Channel - A variation of the rock channel is the use of large diameter rip
rap stone stabilized with lean concrete grout for a channel liner. This 'method has been
utilized on several projects in Dallas recently with good results. The final product is
more cost effective than rock, yet has much of the same aesthetic appeal in a project
such as this. This may l~ an alternative worth considering.
JONES & CARTER, INC.
1-2B-1996 2:08PM FROM JONES/CARTER-DALLAS 21AA883882 P. 6
Nor each of the areas within the park proposed to have erosion control, we have considered
each of these alternatives. Based upon the pros and cons stated above as well as financial
considerations, we recommend the following:
· Upstream of the pond we r~conunend consideration of a washed concrete channel liner,
the construction of rock walls and channel flowline or the rip rap stone channel. Each
of these alternatives will address safety concerns near the playground, aesthetic concerns
tO maintain the natural bcau~ of the area, and engineering concerns for erosion control
and mainte~nancc. For the purposes of this report, we recommend the rip rap stone
charmcl as thc first choice in order to balance aesthetics and fiscal responsibility.
· For the lake edge we recommend consideration of the installation of a gcotextile fabric
or the construction of a rock wall similar to the ones installed throughout the city.
Given the amount of traffic the park r~cives from small children, we believe that safety
concerns outweigh aesthetic considerations in this particular case. Therefore, our first
recommendation would be thc installation of a geotextile fabric or grid along the
shoreline during the removal of the silt from the pond. This imtallation will require the
level of the pond to be lowered somewhat in order to place the gcotextile below the
permanent water line to receive maximum benefit from its use.
· Downstream of the pond is a very similar situation to upstream of the pond regarding
aesthetics, safety and erosion concerns. Our recommendation is somewhat different for
this location, however, because of the existing rock drop structure and bridge at Bethel
School Road. Therefore, we recommend the installation of a rock channel lining
downstream of the pond to match the existing drop structure.
The tohal project cost of the erosion control measures is anticipated to be approximately
$49, I62, see Appendix A for the detailed Opinion of Probable Construction Cost.
Corps of Engineers Permit Requirements
Upon completion of the preliminary engineering documents, we shall meet with
representatives of thc Corps of Engineers to review the project and determine if there is a
need for a Section 404 Wetlands Permit. Based upon discussions with Corps of Engineers
representatives, it is our understanding that this project may not require a permit. However,
the information that must be submitted in order for the Corps to make such a determination
is essentially the same as that for a permit application. Upon approval by the City of a
course of action for the proj~t we shall meet with the Corps and prepare the necessary
submittals prior to the final report. Considering the 60 to 90 day r~vicw time for such a
determination and/or permit, we r~commend that this step be taken immediately after
approval of the preliminary permit in order to minimize the potential impact upon the
construction phase of the project.
JONES & CARTIilR. I,NIC.
1-2~-1~96 2,08Pf-1 FROH JONES/CARTER-DALLAS 21~883882 p. 7
Append~ A
EJONES & CARTER. INC.
Consu~['ng Engineers
Engineer's Opinion of Probable Construction Cost
Project: Duck Pond Park Improvements Date: 12/8/95
Client: City of Coppell
J&C No. D0001-001
Reference: In-Sim Pond l~xcavation
Rcm Unit
No. Description Qty. Units Price Total
1 Mobilization I EA $1,000.00 $ 1,000.00
2 Temporary Low Water Dam '35 CY $ 15.00 $ 525.00
3 Drainage Diversion 1 /,3 $2,500.00 $ 2,500.00
4 Site Fcncing ~00 LF $ 7.50 $ 3.750.00
5 In-Sim (Wet) Excavation 4000 CY $ 10.00 $ 40,060.00
6 Hauling & Material Disposal 4000 CY $ 4.00 $16,000.00
-' $~btotal $ 63,775.00
15% Contingencies $ 9,566.25
._ ' ..... Total[ $ 73,341.25
Page I
- JONES & CARTER, INC.
1 -2S-1996; 2:09Pi'.1 FROM JONES/CARTER-DALLAS 214~883882 P. 8
i
Appeadix A
r JONES & CARTER. iNC.
"' Consulting Engineers
Engineer's Opinion of Probable Construction Cost
J Project: Duck Pond Park Improvements Date: 12/8/95
Client: City of Coppell
j J&C No. D0001-001
Reference: Dry Pond Excavation
I
Item ' Unit
I No. Description Qty. Units Price Total
1 Mobilization 1 EA $1,000.00 $ 1,000.00
i 2 Temporary Low Water Dam 35 CY $ 15.00 $ 525.00
3 Drainage Diversion I LS $2,500.00 $ 2,500.00
4 Site Fencing 500 LF '$ 7.50 $ 3,750.00
5 Dry Excavation- 4000 CY $ 5.00 $ 20,000.00
6 Hauling & Material Disposal 4000 CY $ 3.00 $12,000.00
Subtotal $ 39,775.00
j .. 15_~ Contingencies $ 5,966.25
TotnlJ $ 45,')41:25
J
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j -- - JONE8 & CARTER. INC.
1-2B-1996 2:09P~-t FROM JONES/CARTER-DALLAS 2]~A883882
Appendix A
jC
Consulting Engineers
Engineer's Opinion of Probable Construction Cost
Project: Duck Pond Park Improvements Date: 12/8/95
Client: City of Coppell
J&C No.
Reference: Erosion Control
Item Unit
No. Description Qty. Units Price Total
1 Rip-rap Channel - Upstream 500 SY $ 30.00 $15,000.00
2 Geotextile Fabric - Shoreline 925 SY $ 18.00 $16,650.00
3 Rock Channel - Downstream 220 SY $ ~'5~00 i '9,900.00
$ Dry Excavation 2A0 CY $ 5.00 $ 1,200.00
" ' St~b~tal' $42,750.00
15% Contingencies $ 6,412.50
.... .T0.talI _$ "
!
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i .... JONES & CARTER. INC. -- -